In the prior art it has been a common practice to provide burn-in testing of a laser diode before final assembly into a finished product. The reason for this is that it has been found that a large majority of "near-term" failures of electronic equipment occur within the first few hours of operation. To prevent destruction of the laser diodes during the burn-in process (and in later "normal" operation), it is necessary that the heat generated in the laser action be dissipated in some type of heat sink. To facilitate positioning (focusing) of the laser diode in a finished product, it is desirable that the diode be accurately aligned or positioned with respect to the edges of the heat sink base. While this can be accomplished in a manual operation, it can be very time consuming. Further, it is desirable to test the laser diode to make sure that its characteristics fall within prescribed ranges before using it in an assembled product. Since an individual chip is very small and somewhat fragile, it is very time consuming to accomplish the parameter testing prior to final assembly. Discovery that the chip does not meet specified requirements at this stage results in the disposal of the finished product as waste.
The problems outlined above have been solved by the present inventive concept which involves the production of a plurality of semiconductor chips usable as heat sinks defined on a semiconductor wafer through a photolithographic process. As long as the wafer has a crystalline structure which causes the surfaces to be &lt;100&gt; orientated, a pattern of V-grooves can be etched into the surface wherein the vertices follow the &lt;110&gt; crystallographic planes of the semiconductor wafer and at the proper point in manufacture, the array of heat sink chips can be disassembled into individual chips by fracturing the wafer chips along the V-grooves. Since the circuitry on the heat sinks has been photolithographically defined using the same process as that used to define the V-grooves, the edges of the individual chips are accurately registered with respect to the circuitry. Individual laser diodes can be accurately positioned on a given circuit path on a wafer using mechanical automated procedures and solder reflow techniques. With the proper design of the electronic circuitry on the wafer, a large plurality of chips and their associated laser diodes can be serially interconnected to perform mass burn-in of the diodes. If the photolithographic techniques are used to identify each of the specific chips on a wafer, not only can automated techniques be used to test the individual chips in the array for operability and characteristic range compliance, but the parts failing to pass test requirements can be readily identified and disposed of prior to assembly of the remaining parts in a finished product.
It is thus an object of the present invention to reduce the cost of producing a finished product incorporating a laser diode on a heat sink.